Field of the Invention
The invention relates to a method and system for treating a substrate and, more particularly, to a method and system for performing neutral beam activated chemical processing of a substrate.
Description of Related Art
During semiconductor processing, plasma is often utilized to assist etch processes by facilitating the anisotropic removal of material along fine lines or within vias (or contacts) patterned on a semiconductor substrate. Examples of such plasma assisted etching include reactive ion etching (RIE), which is in essence an ion activated chemical etching process.
However, although RIE has been in use for decades, its maturity is accompanied by several issues including: (a) broad ion energy distribution (IED), (b) various charging-induced side effects; and (c) feature-shape loading effects (i.e., micro loading). One approach to alleviate these problems is to utilize neutral beam processing.
A true neutral beam process takes place essentially without any neutral thermal species participating as the chemical reactant, additive, and/or etchant. The chemical process, such as an etching process, at the substrate is activated by the kinetic energy of the incident (directionally energetic) neutral species and the incident (directionally energetic and reactive) neutral species also serve as the reactants or etchants.
One natural consequence of neutral beam processing is the absence of micro loading since the process does not involve the effect of flux-angle variation associated with the thermal species (which serve as the etchants in RIE). However, an adverse consequence of the lack of micro loading is the achievement of an etch efficiency of unity, i.e., the maximum etching yield is unity, or one incident neutral nominally prompts only one etching reaction. Conversely, the abundant thermal neutral species (the etchant) in RIE can all participate in the etching of the film, with the activation by one energetic incident ion. Kinetic energy activated (thermal neutral species) chemical etching can therefore achieve an etch efficiency of 10, 100 and even 1000, while being forced to live with micro loading.
While many attempts have been made to cure these shortcomings, i.e., etch efficiency, micro loading, charge damage, etc., they still remain and the etch community continues to explore novel, practical solutions to this problem.